rhizome

rhizome (rĪˈzōm) [key] or rootstock, fleshy, creeping underground stem by means of which certain plants propagate themselves. Buds that form at the joints produce new shoots. Thus if a rhizome is cut by a cultivating tool it does not die, as would a root, but becomes several plants instead of one, which explains why such weeds as Canada thistle and crabgrass are so hard to eradicate. Ginger, the common iris, trillium, and Solomon's-seal all have rhizomes. True arrowroot is starch from the rhizome of a West Indian plant. See perennial.